Many industrial and commercial buildings are now being constructed with a plurality of ducts located in the floors of such buildings. In a typical arrangement, the ducts extend parallel to each other and are spaced at predetermined intervals. Each duct contains a number of communications and power cables. To provide interconnection of these cables to various communications instruments such as telephone desk sets, to electrical power outlets, and the like, an electrical termination is provided in proximity to and communicating with one of the ducts at each desired location.
Referring now to FIG. 1, which illustrates a typical such electrical termination of the prior art, a floor 10 has an upper floor surface 12, with a substantially cylindrical aperture 14 extending from upper surface 12 through floor 10 and into a duct 16 in which a plurality of cables, such as cable 18, are located. Although duct 16 is illustrated in FIG. 1 as comprising a metallic, rectangular duct, it may in practice comprise any passageway within or underneath the floor 10 through which cables such as cable 18 extend. Typically, the cylindrical aperture 14 is formed in floor 10 at a location aligned with duct 16 where a telephone outlet or electrical power outlet is desired. The aperture 14 may be formed in place when the floor 10 is constructed, or may be formed at a later time by cutting out the floor 10 by the use of a hole saw or like apparatus. In most cases, an internally threaded cylindrical sleeve 20 is pressed into the aperture 14, with the aperture 14 being closed, if the electrical termination is not to be used, by an externally threaded disc, not illustrated, engaging sleeve 20. The top of this disc is flush when installed with the upper surface 12, so that passage across the floor surface 12 is not obstructed.
When the electrical termination is to be used, the disc is removed and a cable such as cable 18 pulled up through aperture 14 from the duct 16. An externally threaded conduit or nipple 24 is then threaded into an internally threaded aperture of a substantially cylindrical adapter 22 whose diameter approximates that of the sleeve 20 and which has external threads thereon for engaging the corresponding threads of the sleeve 20. The cable 18 is pulled through the conduit 24, and the assembly including adapter 22 is then threaded into the sleeve 20, with the upper end of the conduit 24 protruding above the floor surface 12. A base member or plate 26 having a central aperture is then placed over the protrusion of conduit 24 and is secured to the floor 10 by a nut 28 through which the cable 18 is passed and which is threaded onto the conduit 24 to press the base member or plate 26 against the floor surface 12. To make an electrical interconnection with an instrument such as a telephone desk set, a cable 34 from that desk set is passed through a grommeted aperture 32 in the side of the housing 30, with the conductors in the cable 34 being interconnected with a corresponding number of conductors in the cable 18 by means of a plurality of splices 36. Alternatively, electrical connectors may be used in place of splices 36, or, the cable 18 may itself be pulled through the grommeted aperture 32 and terminated in an electrical connector external to the housing 30. The housing 30 is secured to the base member or plate 26 by a plurality of fasteners 38.
Although functioning to provide electrical interconnection between a telephone desk set and the like and a cable located within the duct, the electrical termination of the prior art as typified by that illustrated and discussed with respect to FIG. 1 has proved disadvantageous in many respects.
As an example, the electrical terminations of the prior art are often difficult to install. The internal threads of the sleeve 20 often become encrusted with concrete and other foreign material, especially where it is installed at the time the floor 10 is constructed, which foreign material must be removed before the assembly including adapter 22 can be installed. Time and skill are also required to properly assemble the numerous components of the prior art electrical terminations and to make the necessary electrical interconnections, such as by splices 36 or otherwise. Accordingly, the services of a trained and competent technician are almost always required on the initial installation of such a prior art electrical termination. Most important, such services are also required whenever the instrument, such as a telephone desk set, utilizing a particular electrical termination is to be moved or changed. In many industrial plants which have a very large number of telephone desk sets which are constantly being disconnected and connected due to changes in the physical location of personnel working in that plant, significant costs resulting from the services of trained technicians are incurred in effecting such disconnections and connections with the electrical terminations of the prior art.
As can be readily appreciated by those skilled in the art, a prior art electrical termination such as that illustrated and discussed with respect to FIG. 1 is costly insofar as it includes a number of separate components, each of which requires an individual manufacturing step for its formation. Moreover, a prior art electrical termination as in FIG. 1 often times presents a safety hazard when installed, since the housing 30 protrudes above the floor surface 12, thereby providing an obstruction to passage.
It is therefore an object of this invention to provide a receptacle functioning as an electrical termination for floor ducts which overcomes the disadvantages previously stated of the prior art.
It is a further object of this invention to provide such a receptacle which is inexpensive to manufacture and which includes fewer components than the electrical terminations of the prior art.
It is yet a further object of this invention to provide such a receptacle which is easy to initially install, and which also allows a relatively unskilled person to connect and disconnect an instrument such as a telephone desk set at the receptacle.
It is another object of this invention to provide such a receptacle which is rugged in construction, which is substantially liquid-resistant, and which is substantially flush with a floor surface when installed.